As multi-functional electronic devises become popular, a compact and slim type electronic device is demanded as exemplified by a portable phone, and a switch having a light and comfortable touch feeling is widely used for various electronic devices, many mounted on a side of the devices.
A conventional push switch used in the electronic devices is explained with referenced to FIGS. 7 to 10. FIG. 7 is a cross sectional view of a conventional push switch; FIG. 8 is an exploded perspective view of the conventional push switch; FIG. 9 is a cross sectional view showing an operation status of the conventional push switch; and FIG. 10 is a side view of the conventional switch showing its mounting status.
As shown in FIGS. 7 to 10, the conventional push switch includes switch case 101 made of insulating resin in a square shape having upper opening 101A and concavity 101B in substantially a round shape recessed from a bottom plane of upper opening 101A. Inside a bottom plane of concavity 101B, center fixed contact 102 is disposed at its central part and a pair of outer fixed contacts 103 disposed at an outer parts of the concavity by insertion molding symmetrically with respect to center fixed contact 102. Terminals 104 and 105 are drawn out of a side wall of switch case 101 connected to center fixed contact 102 and outer fixed contacts 103.
Movable contact 106 made of an elastic thin metal plate formed in an uplifted round dome shape is placed on outer fixed contact 103 with its lower peripheral part put on the fixed contact. Flexible protective sheet 107 of an insulating resin film is attached to the bottom plane of upper opening 101A of switch case 101, covering an upper plane of concavity 101B which contains movable contact 106.
On protective sheet 107, operating body 108 is placed in a horizontally movable manner in back and forth direction. Operating body 108 has operating part 108A extended from a front side outer wall of switch case 101, driving part 108B which is elastically deformable and formed in a bar shape having pressing part 108C which has a tip extended toward a center portion of upper opening 101A of switch case 101, and sliding guide 108E in a flat shape surrounding driving part 108B through notch 108D in substantially a U-shape, and they are all one piece resin molded.
The conventional push switch includes cover 109 of a metal plate, fixed to switch case 101, covering operating body 108 and restricting an upward movement of operating body 108. Cover 109 is put on switch case 101, closing upper opening 101A of switch case 101. Cover 109 is engaged with two outside walls of switch case 101 crossing an other outside wall at right angles where terminals 104 and 105 are extended. Namely, cover 109 has engaging parts 109A extended downward, one toward a front side wall where operating part 108A is positioned and an other toward an opposing rear side. Engaging part 109A is engaged with interlocking projection 101C formed in the walls, attaching the cover to switch case 101.
On an upper central portion of cover 109, a pair of slits 109B is formed, and a portion between the pair of slits 109B is obliquely bent down forming inclined part 109C. As cover 109 is installed on switch case 101, inclined part 109C of cover 109 is placed in notch 108D of operating body 108, in which an upper part of pressing part 108C as the tip of driving part 108B of operating body 108 comes into contact with a front side plane of inclined part 109C.
The conventional push switch is thus constituted. Next, a working mechanism of the switch is explained.
First, when operating part 108A of operating body 108 is pushed forward, operating body 108 is horizontally moved to a rear side of the switch. Driving part 108B is then elastically deformed at its base part and its tip is sled obliquely downward along a slanted plane of inclined part 109C of cover 109. Accordingly, pressing part 108C, the tip of driving part 108B pushes down a top portion of movable contact 106 in a dome-like shape through protective sheet 107. When downward pushing force of movable contact 106 exceeds a specified value, the dome-like top portion of movable contact 106 is elastically turned around generating a crisp feeling and pointing downward as shown in FIG. 9. Thus, an under center part of the movable contact 106 touches a top portion of center fixed contact 102, turning the switch on.
Following, when the push force applied to operating body 108 is released, the dome-like portion of movable contact 106 restores its original shape with a comfortable feeling, pointing upward. With this self-restoring power of movable contact 106, pressing part 108C that is the tip of driving part 108B is pushed upward. The tip of pressing part 108C moves back obliquely upward along inclined part 109C helped by a self-restoring power of elastically bent driving part 108B. As a result, operating body 108 is horizontally pushed back to a front side with sliding guide 108E sliding on protective sheet 107 adhered to upper opening 101A. Thus, the switch returns to the original off state, as shown in FIG. 7.
The conventional push switch operates when pushing operating part 108A of operating body 108 is horizontally pushed. The switch is generally mounted on wiring board 110 and soldered to wiring board 110 so as operating part 108A to protrude from an end portion of wiring board 110 as illustrated in FIG. 10.
As a prior art document related to the applied invention, Unexamined Japanese Patent Publication No. H11-39987 and Unexamined Japanese Utility Model Publication No. H5-1126 are publicly known, for examples.
The conventional push switch, as illustrated in FIG. 10, is attached in a state where operating part 108A is protruded from the end portion of wiring substrate 110. Because of this arrangement, operating part 108A protruded from the end of wiring substrate 110 may bump into or it may hook some object, applying an unexpected load or damaging operating part 108A.
To enhance strength of the operating part, the operating body can be made thicker, but it makes the push switch thicker going against a market requirement for thin type product.